From the Guidelines
A concerning low level of urine output is generally considered to be less than 0.5 mL/kg/hour in adults, or less than 400-500 mL over 24 hours (oliguria). This threshold is important because it may indicate kidney dysfunction or inadequate blood flow to the kidneys. For children, the concerning threshold is lower at 0.5-1 mL/kg/hour, while for infants it's 1-2 mL/kg/hour. Several conditions can cause reduced urine output, including dehydration, blood loss, heart failure, kidney disease, urinary obstruction, or certain medications. When low urine output occurs, healthcare providers typically assess for underlying causes through physical examination, blood tests, and sometimes imaging studies. Treatment depends on the cause but often includes intravenous fluids to restore volume, addressing any obstruction, or treating the underlying condition. Persistent oliguria requires prompt medical attention as it can lead to waste product accumulation in the blood and electrolyte imbalances that may become life-threatening if not addressed, as supported by the most recent study 1.
Some key points to consider when evaluating low urine output include:
- The definition of acute kidney injury (AKI) and its stages, as outlined in the Kidney Disease: Improving Global Outcomes (KDIGO) criteria 1
- The importance of serum creatinine and urine output in assessing renal function, as discussed in the study by Angeli et al. 1
- The need for prompt medical attention in cases of persistent oliguria to prevent complications, as emphasized in the study by the International Club of Ascites 1
Overall, the evaluation and management of low urine output require a comprehensive approach that takes into account the underlying causes and the patient's overall clinical condition, as supported by the evidence from recent studies 1.
From the Research
Definition of Low Urine Output
- Low urine output, also known as oliguria, is a condition where the urine output is less than 400 mL per 24 hours in adults 2.
- Oliguria can be an important sign of kidney dysfunction and should be evaluated in conjunction with other factors such as hydration status and use of drugs 2.
Concerning Levels of Urine Output
- A urine output of less than 0.5 mL/kg/hour for 12 hours is considered a concerning level and may indicate acute kidney injury (AKI) [(3,4,5,2,6)].
- Reduced urine output for a certain number of hours may be an important sign of kidney dysfunction, and it is essential to evaluate it in conjunction with other factors 2.
Evaluation and Management
- The evaluation of low urine output should take into account patient characteristics, nature of the acute illness, and trajectories, as well as risks and benefits of fluids 6.
- Fluid administration should be individualized, and excessive fluid administration should be avoided, as it is associated with poor outcomes, including the development and progression of AKI [(4,5,6)].
- Oliguria alone should not be viewed as a trigger for fluid administration, and fluids should only be administered until intravascular hypovolemia has been corrected and euvolemia has been achieved 6.